Recover GM Delco E98, E39, E39A ECMs with Shadow Password in Boot

If you killed GM ACDelco E98, E39, E39A, E83, E84 etc ECM modules or it is locked by the tuner, you can recover ECMs with a  Shadow Password. This is the password for the boot mode.

Gm Delco Ecm Shadow Password 2 Gm Delco Ecm Shadow Password 3

What is the shadow password used for?

This is the password to enter recovery mode. Each instance of the module has its own password.

If the ECM module died during programming and does not respond to commands or if, for example, the tuner protected the block from reading, knowing the password you will be able to read and write the correct firmware etc.

The module block has a shadow memory page.

While the block is alive and you have access to it, you can read the shadow password.

We have encountered a few instances of needing the password, usually quicker to program a donor ecu to car. Recover our bricked ECU saving buying and programming another.



How to Find Shadow Password to Unlock Bricked GM Delco E98 E39 E39A etc?


The best way you read it with I/O Terminal, M&D Flasher or OBDSTAR DC706/G3 with Shadow Password. This is the only way for Recovery.
When you have no Shadow Password and lost Communication the PCM is Dead.

No other tools (Fg Tech, Kess, Autotuner, CMD, PCM Flash, Xhorse Multi Prog) can do this Job (Read Shadow Password). No tool can recover them without shadow password, even Flex. Flex in boot ask for password, and there is no options to read it.


With I/O terminal or DC706, they are able to read emulated eeprom, MPC Flash and shadow password.

One of our customers did a Delco E39 ECM yesterday with the dc706, it does save a file with a shadow password. That’s one big advantage over I/O terminal. You can pull the shadow password by clicking read flash. This password is needed if you ever brick the ECM. If you break it and then you will not be able to connect to that ECM with the shadow flash password, you can open it up then connect it in boot mode and then you will be able to restore that ECM. DC706 works well on Delco ECMs. It has immo resets on some of them. reads shadow password and all.

Obdstar Dc706 Gm Delco Shawdow Flash

You can also use the OBDSTAR to read, then multi prog to modify VIN, rewrite with Obdstar.

For example: when clone e39 ecu with Multiprog and it is asking for 16 digit password. It asks for shadow password typically for boot.

You can pull the password with the io terminal and try reading with multiprog to test and confirm.

Gm Delco Ecm Shadow Password 4

Here we share a recovery guide of AC Delco E98 ECM.

Device used: I/O Terminal & Alientech KESS3.

ACDelco E98 – bricked with a Genuine Tool!
Customer tried everything to recover but no joy…Ecu is completely Unresponsive!
Even Alientech Support were no use as the Bench Protocol wasn’t working either.
Ac Delco Ecus are commonly known for locking up when writing to them.
Recovery on them is a pain, as these Delco units hold something called a Shadow Flash Password.
Without this, Boot mode recovery is NOT possible.
However, with the help of I/O Terminal- we are able to calculate Shadow Flash Passwords from the Label of the Ecus on the Delco E98, E39 and E39A.

How to get a shadow password? After you are hooked up click on connect, then after you are connected click on read shadow password. it’s easy.
With this, we opened the Ecu cover, and loaded Boot Recovery Mode.
Analysing the Data, we realised that the tool erased Block 0x4FB00 to 0x5FFF0 when programming and mustnt of restarted the writing process.
Took the original client read and rebuilt the data into a new fix file.
After Flashing this, we can restore all communication with the Ecu.
We then went one step further and flashed the clients Mod file to the Ecu with the Latest Kess3 to ensure the Ecu was able to read and write properly going forward.

Recover Gm Delco E98 Ecm 1

Recover Gm Delco E98 Ecm 2 Recover Gm Delco E98 Ecm 3 Recover Gm Delco E98 Ecm 4 Recover Gm Delco E98 Ecm 5 Recover Gm Delco E98 Ecm 6 Recover Gm Delco E98 Ecm 7 Recover Gm Delco E98 Ecm 8 Recover Gm Delco E98 Ecm 9 Recover Gm Delco E98 Ecm 10 Recover Gm Delco E98 Ecm 11 Recover Gm Delco E98 Ecm 12 Recover Gm Delco E98 Ecm 13 Recover Gm Delco E98 Ecm 14


Read more:

OBDSTAR DC706 vs I/O Terminal

How to Virgin GM ACDelco ECUs?